A World War I-era German submarine (commonly referred to as a U-boat) filled with 23 bodies was discovered in the waters off the coast of Belgium, officials said Tuesday.

The intact, century-old vessel was found by researchers on the floor of the North Sea bordering the region of West Flanders, Governor Carl Decaluwe told the Associated Press.

“It’s quite amazing that we found something like this,” Decaluwe said. “The impact damage was at the front, but the submarine remains closed and there are 23 people still onboard.”

Damage to the front of the U-boat suggests that it struck a mine with its upper deck, according to the AP. Other than the mangled front, the only other damage to the ship that researchers found was two destroyed torpedo tubes.

The 88-foot-long U-boat has collected a lining of barnacles and seaweed over the years, as well as fishing gear and nets, video obtained by the AP shows.

The exact location of the sub’s discovery remains unknown as Decaluwe declined to comment until the site has been protected. For now, he has reached out to German officials so they can figure out what to do with the human remains, according to the AP.

The North Sea was patrolled by a number of submarines on both the Allied and Central sides during World War I. German U-boats would target Allied warships and cargo carriers launched from Bruges on Belgium’s coast.

The latest discovery is the 11th World War I-era wreck to be found in Belgian waters, according to the AP.